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Equation for probability

  1. Jul 5, 2011 #1

    I'm trying to remember back to my high school / college days and have no idea where to start.

    Basically, I'm trying to find probability in numbers for a specific range. I'd like to figure out an equation so I can plug it into software. Here are my sample values below:


    So this line will basically never hit 1. I can't for the life of me figure out what to search for on google for this, I remember doing something easy back in school, but it's been a good 20 years, and actually need to use it.

    Any direction would be great.

  2. jcsd
  3. Jul 5, 2011 #2


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    Homework Helper

    What's the exact problem? I can't really tell what your question is. What does it mean to "find probability in numbers for a specific range"? What are those sample values you listed? What exactly are you trying to find the probability of? etc..
  4. Jul 5, 2011 #3
    There's a system called the Elo Rating System (http://en.wikipedia.org/wiki/Elo_rating_system). I'm trying to figure out the probability of Player A vs Player B. I played around in excel using Ln which is sort of what I'm looking for based off of a table similar to http://www.ascotti.org/programming/chess/elo.htm [Broken]

    I was hoping to simplify it the best I could.
    Last edited by a moderator: May 5, 2017
  5. Jul 6, 2011 #4
    If you really want there to be a horizontal asymptote at y=1, log won't do the trick since it's unbounded. Maybe something more along the lines of
    f(x) = \frac{x+1}{x+2} = 1 - \frac{1}{x+2}
    would work, since it does have a horizontal asymptote.
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